A spheres-in-sphere structure for improving protein-loading poly (lactide-co-glycolide) microspheres

In present study, protein loaded poly (lactide-co-glycolide)/chitosan microspheres (PLGA/CS MSs) with spheres-in-sphere structure were prepared in order to weaken the burst release of protein from PLGA microspheres (PLGA MSs) and to buffer acidic micro-milieu. The PLGA MSs and PLGA/CS MSs were characterized in terms of their size distribution, morphology, drug-loading rate, zeta potential and physical-chemical properties. The incubation experiments of PLGA MSs and PLGA/CS MSs; were manipulated in PBS solution at pH 7.4, 37 degrees C to monitor the release of BSA and the vehicles degradation. The release kinetic of BSA was illuminated mainly based on the degradation processes of the matrices. External CS crusts were proved to strikingly improve the release kinetic of the model protein by reducing initial burst release and extending continuous release while acting as a diffusion barrier. Moreover, using PLGA/CS MSs could avoid the decrease of pH value resulted from the acidic products of PLGA MSs because of the effective buffer action of the basic groups in CS. The results demonstrated that the spheres-in-sphere structure is an effective way to control the initial burst release of protein and to overcome the acidic problem of protein-loading PLGA MSs. (C) 2009 Elsevier Ltd. All rights reserved.